Set it up in an equation. 1) 45+5x=9x+9 2) Get x on ONE side: subtract 5x from both sides 3) bring down the equation: 45=4x+9 4) get x by itself: subtract 9 from both sides 5) bring down the equation: 36=4x 6) get x by itself: divide 4 from both sides 7) bring down the equation : 9=x 8) put 9 in the place of x : 9(9)+9 9) 9•9=81 10) 81+9=90 So the exterior angle is equal to 90.
